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Atomic Concepts

Subatomic Particles Charge Mass Location

proton + 1 1 amu nucleus

electron – 1 1/1836 orbits

neutron 0 1 nucleus

NOTE: charge of nucleus = #p

Isotopes – atoms of the same element, which differ in the number of neutrons; have the same

atomic no., but a different mass number

12.0000 13.0335 WEIGHTED AVERAGE ATOMIC MASS

C C 0.9889 (12.000) + 0.0111(13.0335) = 12.011 amu

6p+ 6e

- 6p

+ 6e

- The atomic mass will be closest to the isotope with the

greatest percentage.

-------------------- ------------------

6n◦

7n◦

relative abundance:

98.89% 1.11%

Electron Configuration – the arrangement of electrons in the energy levels

(orbits, shells) of an atom in the ground state.

___________ distance from nucleus, ___________ energy of electron

In the ground state, electrons fill the lowest available energy level, starting from

the shell closest to the nucleus.

Complete Energy Levels: 2-8-18-32 …. 8 max “valence” e- ----------------------------------------------------------------------------------------------------------------------------

atomic mass number (#p + #n) 12.011

- - C atomic number (#p) 6p

+ 6e

-

----------------------------------------------------

(#n) 6n◦

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“Ground State” Possible “Excited State”- move only one e- further away from

nucleus

2-8-3 2-7-4 or 2-8-2-1 or 1-8-4 , but not 3-7-3

Metals- lose electrons forming (+) ions Nonmetals – gain electrons forming (-) ions

Na Na +1

O O-2

2-8-1 2-8 2-6 2-8

The ions have a “Noble Gas” electron configuration = 8 electrons in the outermost shell.

Lewis (e- Dot) Structure – represents only the valence electrons; start with the first 2 dots

together in the 12 o’clock position, continue placing electrons in the remaining positions (3, 6 &

9 o’clock), one at a time, until you have two in each; the max is an OCTET.

Rutherford’s Gold Foil Experiment Wave Mechanical Model for explaining spectra of elements with

multi-electron atoms

An atom is mostly “empty” space;

its “nucleus” is very small, but massive,

and it’s positively charged.

Orbital – the region around the nucleus of an

atom where an electron can most probably be

found; aka “electron cloud”.